1. Field of the Invention
The present invention relates to a camera module.
2. Description of Related Art
In recent years, a camera module having a lens and a solid-state imaging device is mounted on various devices including a cellular phone. The solid-state imaging device is directly or indirectly fixed to a mount of the camera module. The imaging quality of the camera module largely varies depending on a relative position of the solid-state imaging device and the lens. Accordingly it is important to accurately position the solid-state imaging device and the lens.
An example of a configuration of a camera module is disclosed in Japanese Unexamined Patent Application Publication No. 2005-347397. In the camera module disclosed in Japanese Unexamined Patent Application Publication No. 2005-347397, a solid-state imaging device is formed over a semiconductor substrate. The solid-state imaging device is sealed by a spacer or a cover glass disposed over the semiconductor substrate. A lens holder is mounted over the cover glass. A concave portion is formed in the lens holder. The cover glass is fit to the concave portion of the lens holder, and fixed to the lens holder by an adhesive.
In the configuration shown in Japanese Unexamined Patent Application Publication No. 2005-347397, the cover glass is fit to the concave portion of the lens holder as described in the foregoing. To accurately position the cover glass and the lens holder, the surface contacting the cover glass of the lens holder should be flat, and the flatness of the surface needs to be improved. Without improving the flatness in the surface of the concave portion, the solid-state imaging device and the lens can be positioned incorrectly, resulting to largely change the imaging quality. The lens holder is usually formed from synthetic resin. It is difficult to improve the flatness.
Although not disclosed in the Japanese Unexamined Patent Application Publication No. 2005-347397, an optical filter may be provided between the lens and the solid-state imaging device. Generally the optical filter is fixed to the lens holder etc by an adhesive, however as the adhesive adheres to the light-receiving portion such as the cover glass etc, the imaging quality is decreased.
Further, a structure is suggested in which a silicon chip (a solid-state imaging device) and a lens holder are bonded and fixed to a substrate by an adhesive. However in this case, it is difficult to position the lens and the solid-state imaging device due to irregularity in the adhesive and in cutting the silicon chip.